This proposal seeks to elucidate the mechanisms of bone resorption in chronic otitis media. Bone resorption in the ear of animal models will be induced using keratin and by applying pressure using laminaria, an expandable seaweed material. The insertion of laminaria in the ear through the bulla is used to simulate compression, created by keratin debris, resulting in bone resorption in the ear. The pressure induced in the animals will be measured using pressure tranducers in vivo. The pressure will be replicated with microsprings. Resulting bone resorption will be measured using a computerized video microscope to study: a) the total thickness of the otic capsule wall at similar anatomical locations in both control and experimental samples, b) size of the osteoclasts and number of osteoclastic nuclei, c) the thickness of osteoid seams in bone immediately subjacent to resorptive surfaces, d) porosity of subjacent bone, e) osteocytic lacunar size, and f) concentration of collagenase. These animal models will also be used to assess the cellular origin of the bone resorbing factors (collagenase, collagenase stimulators and bone resorptive proteins) by immunocytochemical technique and by using bone resorptive inhibitors, indomethacin and calcitonin. The factors responsible for chronic inflammatory bone resorption will be studied using three principal cells; fibroblasts, macrophages and epidermal basal cells. These cells will be studied separately in tissue cultures and under various conditions to determine the effects of cellular interactions on the production of bone resorbing substances. These bone resorbing substances will be isolated from conditioned media of cell cultures, be purified by chromatography and characterized biochemically and immunocytochemically with antibodies to these bone resorbing substances and quantitatively with the computer assisted microscope.